Active Device transforms and injects power or energy into a circuit. Passive Device utilizes power or energy into a circuit. Examples: Diode, Transistor, SCR, ICs, DC generator, Current & Voltage sources etc. Examples: Resistors, Capacitors, Inductors, Transformer, Motors etc.

The active DI has a built-in buffer or unity gain amplifier that deliver a stronger signal than the passive counterpart. The benefit with a passive direct box is the simplicity of not having to worry about local power, of course isolation and extreme signal handling.